One of the most accomplished women's long distance runners in U.S. history, Jennings was a dominant force in cross country, both in the U.S. and internationally. Jennings has won more U.S. women's cross country titles than anyone in history with nine crowns over a 12-year span from 1985 to 1996. She won three consecutive women's world cross country championship titles from 1990 to 1992. She won the silver medal in that event in 1986 and the bronze medal in 1993. A three-time Olympian, Jennings won the bronze medal in the 10,000 meters at the 1992 Olympic Games in Barcelona. A four-time member of U.S. World Outdoor Championship teams, Jennings medaled at two World Indoor Championships, winning 5,000m bronze in 1993 and silver in 1995. Jennings won 10 U.S. Outdoor Champion titles (3,000m-1988, 1990/5,000m-1996, plus seven 10,000m titles), and set the women's world indoor 5,000m record of 15:22.64 in 1990. Her U.S. 10,000m record of 31:19.89 set in 1992 lasted for a decade.